1. Field of the Invention
This invention relates to rubber pads for electronic percussion instruments, and particularly relates to rubber pads composed of multicolored rubber materials. This invention also relates to methods for manufacturing rubber pads for electronic percussion instruments.
2. Description of the Related Art
Conventionally, various types of electronic percussion instruments have been developed and produced, wherein electronic drums are designed to electronically simulate properties and characteristics of acoustic drums and are constituted by so-called electronic drum rubber pads (simply referred to as rubber pads), so that when users or players strike (or beat) surfaces of rubber pads, which correspond to drumheads of acoustic drums, with sticks, striking intensities are detected by percussion sensors (or impact sensors) such as piezoelectric elements, which are arranged on backsides of rubber pads, to produce detection signals, based on which corresponding electronic sounds (or drum sounds) are to be produced from electronic sound sources.
There are various playing techniques (i.e., executions) in playing acoustic drums, such as normal performance in which players strike normal areas of drumheads, and so-called rim-shot performance in which players strike rims of acoustic drums, for example. In the rim-shot performance, it is possible to produce sounds of specific tone colors, which differ from normal tone colors of acoustic drums that are played in the normal performance. Recently, electronic drums are improved to realize the aforementioned rim-shot performance and the like by incorporating various ideas. For example, it may be possible to arrange percussion sensors called rim switches in proximity to rims of rubber pads, so that strikes of rims are to be detected. Such electronic drums incorporating rim switches have already been developed.
The aforementioned percussion sensors, called xe2x80x9crim switchesxe2x80x9d, may be normally arranged at specific positions (e.g., backsides of rubber pads), other than striking surfaces of rubber pads, in order not to be directly struck with sticks and the like. In addition, the same external design is adapted to both rim-switch-accompanied rubber pads, which are accompanied with rim switches in proximity to rims, and other rubber pads that are not accompanied with rim switches. Therefore, it is very difficult to visually distinguish between them in appearance.
Some electronic drums have both rubber pads accompanied with rim switches and other rubber pads not accompanied with rim switches. For example, an electronic drum set can be accommodated to the player (or user) like an acoustic drum set in such a way that plural rubber pads are arranged around the player. An acoustic drum set may include one or plural drums allowing the player to play rim-shot performance and the other drum(s) basically not used in rim-shot performance. For this reason, the aforementioned electronic drum set may include one or plural rim-switch-accompanied rubber pads and the other rubber pads not accompanied with rim switches. Therefore, it is necessary to make distinctions between two types of rubber pads in appearance.
All rubber pads can be accompanied with rim switches in an electronic drum set; however, this would increase the cost. Therefore, it is reasonable for electronic drum sets to be each manufactured combining two types of rubber pads. That is, it is necessary to make distinctions between them in appearance during manufacture.
Therefore, various methods are developed to make distinctions in appearance between rubber pads accompanied with rim switches and other rubber pads not accompanied with rim switches.
One method for making distinctions is to somehow change external shapes of these rubber pads, wherein prescribed marks are impressed on one of two types of rubber pads during formation, for example. However, this method requires two types of metal molds for use in manufacture of different types of rubber pads, wherein one metal mold is used for producing rubber pads having marks, and the other metal mold is used for producing other rubber pads not having marks. This increases the cost for manufacturing rubber pads.
Another method for making distinctions is to paint or print prescribed colors or marks on one of two types of rubber pads. However, this method may not guarantee sufficient durability because paints or prints may be easily peeled off from rubber pads, which are intensely struck with sticks when players play electronic percussion instruments.
A further method is to perform two-colored formation on two types of rubber pads in such a way that at least rims are formed using rubber whose color differs from that of rubber used for forming the other portions (e.g., pad portions) of rubber pads (including striking surfaces). Thus, it is possible to realize distinctions between rubber pads accompanied with rim switches and other rubber pads not accompanied with rim switches.
According to the aforementioned method, players (or users) can visually distinguish in appearance between rubber pads accompanied with rim switches and other rubber pads not accompanied with rim switches with ease. In addition, this method is advantageous in that both of the two types of rubber pads can be produced using the same metal mold. Furthermore, even when rubber pads are struck intensely, colors of rubber pads are not changed at all; therefore, the aforementioned two-colored rubber pads have sufficient durability.
However, even though rims and pad portions of rubber pads are formed using rubbers of different colors, there occurs another problem in that rubber pads may not be always produced with good external appearance because when rubber pads are each formed in a conventional shape using a conventional metal mold, color differences may not be clearly shown in boundaries between rims and pad portions, which may be intermixed in color.
A manufacturing method of a conventional rubber pad for use in an electronic percussion instrument will be briefly described with reference to FIGS. 5 to 7, wherein FIG. 5 is a cross sectional view showing an example of a conventional metal mold for use in formation of a conventional rubber pad; FIG. 6 is a cross sectional view of the conventional rubber pad, which is formed in two colors using the metal mold of FIG. 5; and FIG. 7 is a plan view showing different color divisions of the conventional rubber pad, in which a rim and a pad portion are colored differently.
In FIG. 5, compounded rubbers are put into cavities 133a and 133b formed between an upper mold 131 (realizing cavities) and a lower mold (or a core) 132 of a metal mold 130, which is then sandwiched between hot plates and is subjected to press formation (or compression formation) realizing vulcanization and pressurization, so that a conventional rubber pad is formed. As described above, two types of cavities, namely, a pad forming cavity 133a and a rim forming cavity 133b, are formed between the upper mold 131 and the lower mold 132. That is, rubbers of different colors are respectively put into the pad forming cavity 133a and the rim forming cavity 133b, wherein they are simultaneously subjected to press formation. Thus, it is possible to integrally form a rubber pad 100 (see FIGS. 6 and 7) in which a pad portion 111 and a rim portion 112 are integrally combined together.
Suppose that the rubber pad 100 is constituted by the pad portion 111 of blue color and the rim portion 112 of black color, for example. In this case, a blue-colored rubber is put into the pad forming portion 133a, and a black-colored rubber is put into the rim forming portions 133b, so that these rubbers are simultaneously subjected to press formation in the metal mold 130. During press formation, the blue-colored rubber and the black-colored rubber may be partially intermixed with each other and infiltrated in color in proximity to a boundary 133c of different-colored divisions between the cavities 133a and 133b. 
For this reason, as shown in FIGS. 6 and 7, a blue-colored region and a black-colored region cannot be clearly distinguished and infiltrate into each other in proximity to a boundary 113 between the pad portion 111 and the rim portion 112. This makes a boundary between rubbers of different colors unclear. Therefore, even when a metal-plate body is covered with the rubber pad 100 to constitute a single pad of an electronic drum, it may be difficult to guarantee satisfactory external appearance in view of the striking surface thereof.
It may be possible to improve external appearances of rubber pads by preventing regions of different colors from infiltrating each other at boundaries therebetween. For example, different materials can be used for regions of different colors respectively. That is, a blue-colored region is made of a blue-colored plastic, and a black-colored region is made of a black-colored rubber.
However, when different materials are used for regions of different colors that join together, it is difficult to guarantee sufficient joining strength therebetween. Therefore, this method cannot be adapted to rubber pads for use in electronic percussion instruments such as electronic drums, in which relatively high impacts are caused to occur due to striking operations using sticks. In addition, this method has a drawback in that the number of steps in manufacture will be increased.
It is an object of the invention to provide a rubber pad for an electronic percussion instrument in which a pad portion and a rim portion are formed using rubbers of different colors respectively, thus distinguishing between a rubber pad accompanied with a rim switch and the other rubber pad not accompanied with a rim switch. In addition, it is an object of this invention to improve the external appearance of the rubber pad for the electronic percussion instrument by preventing regions of different colors from infiltrating each other in a boundary therebetween without deteriorating durability thereof.
It is another object of the invention to provide a method for manufacturing a rubber pad for an electronic percussion instrument, which is produced by two-colored formation using rubbers put into a metal mold with a single press.
A rubber pad of this invention for use in an electronic percussion instrument is produced by integrally forming together a pad portion (including a striking surface) and a rim portion, which are colored differently in two-colored formation. That is, a rubber of a first color is used for forming the pad portion, and a rubber of a second color is used for forming the rim portion. In addition, a groove is formed in a boundary between the pad portion and the rim portion, in which different colors may be partially intermixed together. Due to the provision of the groove, it is possible to reliably separate different colored regions, i.e., the pad portion and rim portion, from each other, which improves external appearance of the rubber pad compared with the conventional rubber pad without substantially deteriorating durability.
In order to realize the aforementioned rubber pad, there is provided a specially designed metal mold in which a partition wall actualizing the groove is arranged between a pad forming cavity and a rim forming cavity, into which rubbers of different colors are respectively put.